Nikola Tesla Institute
Dr. Nenad Kartalović
Hydrogenerator maintenance – Case studies from practice / Permanent Monitoring of Partial Discharges: Experiences In Complex Generator Diagnostics
ABSTRACT: Hydrogenerator maintenance – Case studies from practice
This presentration is dealing with preventive electrical testing for condition assessment of rotating machines (turbo- and hydro-generators, HV motors) which are regular practice of Specialized Laboratory for Insulation System Testing as a part of Laboratory for Testing and Calibration in Electrical Engineering Instutute Nikola Tesla, acredited according to ISO/IEC17025. These are off line elekctrical testing performed on generators and motors at standstil during yearly overhaul period according to valid relevant IEC/SRPS standards and technical recommendation of Electrical Power Company of Serbia (EPS). Rotating machines in electrical power system of Serbia are in prectice of regular preventive testing since 70s of 20th Century. These electrical test are performed on rotating machines, turbo- and hydro-generator and HV motors instald in EPS in regular intervals – Time Based Condition Assessment (TBCA) with the aim of assessing and monitoring the service condition and timely detection of possible defects that could cause breakdowns and outages during operation. Since year 2008 special test data base is established in IEE Nikola Tesla. Since 2008, ETI Nikola Tesla has created a special database in which all the results of off-line field tests are stored as well as results of all older test report whice was entered manualy. In this way, all data was systematized and the basis was created for the improvement and introduction of tools for monitoring trends and evaluating individual operating parameters of the stator or rotor electrical insulation system (EIS) and windings of rotating machines, which is neccessery for transition to Condition Based Maintenance. Several characteristic case studies from the practice of off-line testing hydrogen generators will also be given.
Keywords: Condition Based Maintenance
ABSTRACT: Permanent Monitoring of Partial Discharges: Experiences In Complex Generator Diagnostics
Permanent monitoring of generators during operation is essential for effective facility management and energy production control. The most commonly monitored variables include temperature and vibrations of various generator components. Partial discharge (PD) monitoring is particularly important for assessing the condition of the generator stator’s insulation system. Various stress and aging factors contribute to increased PD activity over the generator’s operational lifespan. If left unchecked, PDs can lead to insulation defects and potential failures. However, they also provide valuable insights into the condition of the insulation system and, indirectly, the overall state of the generator. The advantages of implementing a PD monitoring system are numerous. Firstly, it ensures high-quality data collection, including a large volume of PD data under different operating conditions, synchronized online data from multiple sources, and multi-channel data acquisition. This allows for trend analysis and correlation identification, facilitating the early detection of potential issues due to data coherence. One key benefit of PD monitoring is the automatic alarm notification system, which alerts operators when PD activity reaches or exceeds predefined thresholds. Additionally, remote access allows for configuration adjustments, real-time data review, and trend analysis. The system also enables comprehensive data collection for post-event analysis. By analyzing PD data alongside complex diagnostics results, the risk of failure can be assessed, and maintenance strategies can be optimized. This paper presents practical experiences in diagnosing the condition of generator stator insulation systems, with a significant focus on PD monitoring. The study examines correlations between PD activity and other variables such as vibration, temperature, active and reactive power, among others. Identifiable or confirmable generator conditions include loose coil rods, poor coil head connections, accelerated insulation aging (due to overheating), contamination of insulation surfaces, and other dielectric disturbances.
Keywords: partial discharges, correlations, diagnostics, generator
Biography of the presenter
Nenad Kartalović, PhD, (1960), research associate, Nikola Tesla Electrotechnical Institute, University of Belgrade (INT). The field of work is research and development of methods and devices. He published over 100 scientific and professional articles (380/h=12). Education: Academically, he is an engineer in technical physics and electrical engineering. Doctorate at the Faculty of Electrical Engineering, University of Belgrade (ETF), Department of Microelectronics and Technical Physics. Membership in expert bodies: Member of SC CIGRE Serbia: A1 Rotating electrical machines, A2 Energy transformers, A3 Equipment for transmission and distribution, B1 Insulated cables, D1 Materials and new testing techniques. President of the National Commission for Standards number 15 – Insulation materials. Member of the National Commission for Standards no. 20 – Power cables. Professional experience: During his work at the Faculty of Electrical Engineering, University of Belgrade (1988-2000), he participated in projects in the fields of: energy efficiency; electrical materials, insulation systems; electrical failure, surge protection. During his work at the Nikola Tesla Institute of Electrical Engineering (2003 – ), he was the manager of one project and the manager of five sub-projects as well as one innovation project, which the Ministry financed as part of the technological development program.
